1. Field of the Invention
The present invention relates to a chuck for rotary tools, which chuck has a basic body surrounding the tool's cylindrical chucking shank in the form of a sleeve. The enclosure wall of the basic body, which surrounds a receiving space for the tool's chucking shank, is penetrated by a substantially radial through-hole and has a clamping screw screwed into the through-hole, which clamping screw applies pressure in a screw-in direction to the chucking shank inserted in the receiving space.
2. Background Information
In metal working, rotary tools are clamped into the machine tool by means of a chuck. Preferred are rotary tools with standardized tool shanks. Conventionally, such tool shanks have a flattened area to provide positive locking for torque transmission. Particularly for the use in drilling tools, however, tool shanks are made fully cylindrical without this flattened area since they are cheaper to produce (DIN 1835 A and 6535 A). In such tools, torque is transmitted through an interference fit. The chuck according to the present invention is intended for this latter type of rotary tools with a fully cylindrical chucking shank.
In chucks of the known art for rotary tools which are equipped with fully cylindrical shanks, torque can be transmitted by frictional locking in that a clamping screw applies direct radial pressure to the shank. Such chucks are suitable only for transmitting low torques which frequently are inadequate for drilling work. To increase the torque to be transmitted, it is known, in chucks for tools with fully cylindrical chucking shanks, to embed the shank in a slit sleeve within the basic body of the chuck. The clamping screw which is radially screwed into the basic body applies pressure on said sleeve from the outside, that is, it acts indirectly on the chucking shank. This solution presupposes that sufficient space is available for mounting the sleeve. Moreover, a sleeve means increased building costs.
To eliminate the need for such a sleeve between the clamping screw and the shank, and nevertheless to guarantee a good transmission of torque, it is known on chucks of the known art that a clamping member can be positioned between the clamping screw and the shank in the radial through-hole, which clamping member is mounted so that it cannot rotate around the axis of the hole, but can be displaced in the direction in which it was screwed in. The clamping member applies pressure to the chucking shank with its end, and is pressurized on its reverse side by the clamping screw (GB-29 908;1913). As a result of the mounting of the clamping member in the through-hole so that it can be displaced axially but cannot rotate, it is possible to provide the end surface of the clamping piece that presses against the chucking shank with a surface contour that corresponds to the chucking shank, thus achieving a superficial application of pressure to the chucking shank.
On a similar chuck of the known art, likewise with a clamping piece inserted between the clamping screw and the chucking shank of the tool, the clamping member is embedded in a a captive manner in a receiving space on the end of the clamping screw, so that when the clamping screw is loosened or is unscrewed from the chucking shank of the tool, the clamping member can be extracted and removed along with it (U.S. Pat. No. 4,511,960). This arrangement facilitates the insertion and removal of the chucking shank in the chuck. The captive embedding of the clamping member on the end of the fastening screw, however, requires deformation of the compression screw, and thus requires considerable time, effort and expense in its fabrication. The clamping member also generally rotates along with the clamping screw when it is not in contact with the chucking shank of the tool. The rotational position of the clamping member is thereby undesirably modified.